UM2+Ex: Unable to successfully print test square

[ModernPachinko 0]

We've had our UM2+ Extended for about a yr and it's mostly been great. I've always noticed in the back left corner it curls a bit, but just tended to avoid the area. I've got a bit more time and choosing now to dig into it w/ the help of the experts here :).

 

I grabbed a test square STL from thingiverse, stretched it out and printed it. The first couple layers are great! However, subsequent layers failed (bubble/ripple effect). I've tried with multiple types of filament, leveling the bed, different glass, various Cura settings and I'm tapped. Any thoughts would be greatly appreciated!

 

[gr5 2,167]

I think you have 2 unrelated issues.

 

In these photographs - all the areas that don't look perfect are over extruded a bit.  I could be wrong - it could be that there is something in the layers below to cause it to stick up but if so please show the very first layer instead.

 

The other issue you mention, "back left corner curls".  I assume you mean the corner of the part lifts off the bed?  The glass is not flat.  It's thicker in the middle - this is the nature of how tempered glass is manufactured.  Becuase it's levelled at 3 positions it should be perfect just above the 3 screws.  combine that fact with the fact that the center is highest and you get 2 low spots: one in rear left and one in rear right corners.

 

When the nozzle is a bit too high off the bed then you don't get good "squish" and so the part doesn't stick very well at all.

 

I'm not sure what the solution is.  You could buy some normal glass I suppose.  Or you could reverse bend the bed (but don't break the traces for the heater!) by bending the rear corners up (the glass actually will bend to a flat position with very little force - only an ounce or so is needed). 

 

I guess the simplest thing would be to raise the rear center of the glass by turning the leveling screw a half turn.  You'll get it overly squished in the rear center but it's probably worth it.